Multi-factor authentication is an approach to computerized security procedures that requires the user to provide more than one form of verification to prove their identity in order to gain access to sensitive data or computer systems. Commonly-used forms of verification include knowledge-based verification data (e.g., something the user knows, such as a password or Personal Identification Number) and token-based verification data (e.g., something the user has, such as a private key, security token or smart card). More recently, efforts have been undertaken to use biometric data for security purposes.